Transitive build

Most modules have dependencies, they have their own dependencies etc... - at the end there are modules are independent modules; that is, modules dependent only on the runtime environment or JDK files.

From mathematical perspective, this forms an directed acyclic graph where each vertice corresponds to module or library, and each oriented edge corresponds to a dependency.

For Buildozer, only module dependencies are considered important; depending on a library may bring the requirement to download the library, but not to build anything.